1. Field of the Invention
This invention relates to aqueous dispersions of a low molecular weight, low melting point, water-insoluble polymer, and, more particularly, to a process of making such dispersions for use in water-resistant compositions.
2. Description of the Prior Art
The art has long recognized the need to provide aqueous dispersions of water-insoluble polymers which can be used in water-resistant compositions such as seed coatings, water-based protective coatings, adhesive binders, water-based formulations for water-proofing, suspension concentrates, sustained release formulations, water-based formulations for UV protection, agricultural formulations and personal care products.
Accordingly, it is an object of this invention to provide aqueous dispersions of water-insoluble polymers.
Another object herein is to provide a process for making such aqueous dispersions of water-insoluble polymers.
What is described herein is an aqueous dispersion of (a) 0.1-40% by wt. of a low molecular weight, low melting point, water-insoluble polymer in which the polymer particles have a size  less than 10 microns, and (b) 0.001-30% by wt. of an anionic emulsifier; preferably wherein (a) is 5-30% and (b) is 2-20%; most preferably (a) is 10-20% and (b) is 5-10%. Suitably (a) is a vinyl pyrrolidone copolymer; preferably, (a) is a vinyl pyrrolidone-alkylated or vinyl acetate copolymer.
In the aqueous dispersion of the invention, suitably (b) is sodium lauryl sulfate, calcium dodecyl benzene sulfonate, tristyryl ethoxylated phosphoric acid or salts thereof, polymeric anionic emulsifiers including lignin sulfonate, neutralized methyl vinyl ether maleic acid half-ester, and polyacrylic acid with  greater than 10% acrylic acid, or salts thereof.
In the aqueous dispersion herein (a) suitably, has a molecular weight  less than 100,000, and a pyrrolidone content  greater than 10%.
As a feature of the invention, there is provided a process of making the desired aqueous dispersion by heating the polymer and anionic emulsifier in water at a temperature close to the Tg of the polymer under high shear mixing conditions, suitably at 40-90xc2x0 C., preferably 50-80xc2x0 C., and, most preferably at 60-75xc2x0 C., and wherein the polymer and anionic emulsifier are present in amounts of 1-40 wt. % and 0.001-30 wt. %, respectively.
In accordance with the invention, there is provided herein an aqueous dispersion of a water-insoluble polymer for use in various commercial applications and formulations. The dispersion is made herein by an advantageous process in which the molten polymer is dispersed in an anionic emulsifier and water as a fine suspension. In the preferred embodiment of the invention, the water-insoluble polymer is heated to close to its Tg, then water and the anionic emulsifier are heated and added to the molten polymer while stirring vigorously under a high shear. The resultant dispersion of the polymer is a homogeneous micro-dispersion in which the polymer particles have a size  less than 10 microns, preferably 0.1-2xcexc.
The micro-dispersion thus prepared then can be added conveniently to a particular formulation for use in a commercial application at a suitable dilution ranging from 1:10 to 1:1000.
Suitable water-insoluble polymers include, but are not limited, to the following:
Vinyl pyrrolidone copolymers like alkyl grafted PVP (Ganex(copyright)/Agrimer(copyright) AL 30, 22, 25, WP 660) Agrimer(copyright) VA (PVP-vinyl acetate copolymers).
Others: Beeswax and alkyl vinyl ether-maleic acid half-ester polymers.
Preferred polymer molecular weight:  less than 100,000, and pyrrolidone content  greater than 10%.
Suitable anionic emulsifiers include, but not limited to, low molecular weight sodium lauryl sulfate, calcium dodecyl benzene sulfonate, tristyryl ethoxylated phosphoric acid or salt; polymeric anionic emulsifiers such as lignin sulfonate, preferably with a molecular weight  greater than 6000, methyl vinyl ether-maleic acid half-ester partially neutralized; and water soluble polyacrylates with at least 10% acrylic acids/salts.
Suitable relative amounts of polymer and anionic emulsifier are: polymer 0.1-40%, preferred 5-30%, most preferred 10-20%, in water. Anionic emulsifiers or polymeric anionic emulsifiers: 0.001-30% by weight of the polymer to be dispersed, preferably 0.002-20%, most preferred 0.005-10%.
The temperature of heating is close to the glass transition temperature or molten/softening point, usually between 40-90xc2x0 C., preferably 50-80xc2x0 C., most preferably 60-75xc2x0 C.; and under high shear mixing.
The following examples describe the invention more particularly:
Examples 1 through 18 illustrate the preparation of fine, aqueous dispersions of water-insoluble polymers such as Agrimer(copyright) AL (alkyl-grafted polyvinyl pyrrolidone copolymers) with anionic emulsifiers, and uses of such dispersions.